Russiaâ€™s MiG-31 Foxhound interceptors will stay in service until â€œat least 2028â€ or possibly five or 10 years more, Air Force chief Lt. Gen. Viktor Bondarev said Friday.

â€œWe are satisfied with this aircraft; it performs its functions wonderfully,â€ the general said, adding that as next-generation long-range missiles and aircraft are developed, interception functions could be assigned to newer warplanes as well.

Bondarevâ€™s remarks seem to be a little bit at odds with his comments in April, when he said the Air Force hoped to receive a new long-range fighter-interceptor by 2020 and retire its existing fleet of MiG-31s by 2028. He also spoke out against restarting production of the MiG-31, which was discontinued two decades ago, saying the country needed a totally new interceptor to meet modern requirements.

The Russian Air Force has 122 MiG-31 interceptors in service and more aircraft in reserve, the general said at the time.

The MiG-31, the fastest fighter-interceptor in service anywhere in the world, has recently been the subject of a comprehensive upgrade to the MiG-31BM standard. The Russian Air Force has previously said it intends to take delivery of up to 60 MiG-31BMs by 2020, under a contract signed with United Aircraft Corporation in 2011

MiG-31 is obsoleted by its concept - to knock out missile cariers by reachin them via supersonic jump.

It is expensive and ineffective for now, when the target is not a weapons carier (which unloads in 1000 km from target, which is far beyound the MiG-31 combat radius), but the weapon itself.

In this situation carying more missiles and loitering more time waiting for attack is much more important than 3000 km/h speed for couple dosen of minutes.
That's why intercept is a Su-35 and PAK FA cup of tea and they will eventually change 31-s in the line.

However, Russia is ----ing big and needs quite a large fleet of capable fighters to protect it. So, upgrading still capable 31-s is a wise decision.